Prelims- Environment
1. The European Union’s Copernicus Atmosphere Monitoring Service (CAMS) announced that a hole in the Arctic ozone layer, believed to be the biggest reported, has closed.
2. It was because of a phenomenon called the polar vortex, and not because of reduced pollution levels due to Covid-19 lockdowns around the world.
3. The hole in the North Pole’s ozone layer had reached a maximum extension of around 1 million sq km.
Ozone layer
1. Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere- stratosphere, between 10 and 50 km from the earth’s surface.
2. Ozone is present in the atmosphere in rather low concentrations. Even at places with the thickest layer has not more than a few molecules of ozone for every million air molecules.
3. They perform a very important function of absorbing the harmful ultraviolet radiation from the sun and eliminate a big threat to life forms on earth.
4. UV rays can cause skin cancer and other diseases and deformities in plants and animals.
Ozone holes
1. The ‘ozone hole’ refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.
2. These holes are most commonly the depletion of ozone over Antarctica
3. These keep forming each year in the months of September, October and November, due to a set of special meteorological and chemical conditions that arise at the South Pole, and can reach sizes of around 20 to 25 million sq km.
3. Such holes are also spotted over the North Pole, but due to warmer temperatures than the South Pole, the depletions here are much smaller in size.
Current year
1. This year, the ozone depletion over the Arctic was much larger. The unusual atmospheric conditions, including freezing temperatures in the stratosphere, are believed to be responsible.
2. Cold temperatures (below -80°C), sunlight, wind fields and substances such as chlorofluorocarbons (CFCs) were responsible for the degradation of the Arctic ozone layer.
3. Arctic temperatures do not usually fall as low as in Antarctica. But powerful winds flowing around the North Pole trapped cold air within the polar vortex— a circling whirlpool of stratospheric winds.
3. By the end of the polar winter, the first sunlight over the North Pole initiated strong ozone depletion. But its size is still small compared to the one observed in the southern hemisphere.
4. The closing of the hole is because of the same polar vortex and not because of the lower pollution levels during the coronavirus lockdown.
Ozone recovery
1. As per the Scientific Assessment of Ozone Depletion data of 2018, the ozone layer in parts of the stratosphere has recovered at a rate of 1-3 percent per decade since 2000.
2. At these projected rates, the Northern Hemisphere and mid-latitude ozone is predicted to recover by around 2030, followed by the Southern Hemisphere around 2050, and polar regions by 2060.
Source: Indian Express
